Since physical cell identifiers (IDs) are bound with resource mapping, code resource configuration, frequency hopping, and other mechanisms in a one-to-one manner in a Time Division Long Term Evolution (TD-LTE) system, configuration of the physical cell identifiers plays an equivalent role to planning of scrambling codes in a Time Division Synchronization Code Division Multiple Access (TD-SCDMA) system, and is particularly important in co-frequency networking.
An initial value of a scrambling code in a physical channel is primarily determined by a physical cell identifier, and particularly in a broadcast channel and a control channel, correlation of a scrambling code in the control channel is determined by correlation of the physical cell identifier, no interference in the channel significantly depends upon the physical cell identifier.
Since the physical cell identifiers correspond to sequence index numbers of Primary Synchronization Codes (PSCs)/Secondary Synchronization Codes (SSCs) in a one-to-one manner, that is, the physical cell identifiers are related to distribution of reference signals. In order to avoid interference between reference signals generated in adjacent cells, the physical cell identifiers need to be allocated reasonably so that the reference signals between the adjacent cells are mapped onto different physical resources to thereby reduce interference between the reference signals.
In a real application, if there are identical remainders of the physical cell identifiers MOD 3, then there will be serious interference between the reference signals in the adjacent cells, so the physical cell identifiers are currently allocated generally by following the principle of avoiding the remainders of the physical cell identifiers between the adjacent cells from being identical. In the prior art, in order to avoid the remainders of the physical cell identifiers MOD 3 between the adjacent cells from being identical, the physical cell identifiers are allocated by determining priorities of the adjacent cells according to parameters of a network topology, e.g., distances, direction angles, simulated overlapping of coverage, etc., and then determining the adjacent cells with higher priorities an that it will suffice only if the physical cell identifiers MOD 3 of the adjacent cells with higher priorities are different from those of the present cell. For example, the most closest three adjacent cells are determined as adjacent cells with higher priorities, and it will suffice only if the physical cell identifier MOD 3 of the present cell is different from those of the adjacent cells with higher priorities. However the cells with the strongest interference indeed between them may not be the closest cells due to the topography, building, transmitted power, and other factors, and in this case, the requirement of interference-minimum between reference signals may not be satisfied in the existing physical cell identifiers allocation method.
In summary, the existing physical cell identifiers allocation method may not effectively reduce interference between reference signals.